Shell for blasting cartridges



Oct. 28, 1930. A. w. HELMHOLTZ ET AL 1,

SHELL FOR BLASTING CARTRIDGES Filed June 23, 1928 Patented @ct. 28, 1930ARTHUR W. HELMHOLTZ AND DENT FERRELL, F HARRISBURG, ILLINOIS, ASSIGNORS1'0 SAFETY MINING COMPANY, OF HARRISBURG, ILLINOIS, A CORPORATION OFILLINOIS Application filed June 23,

5 pressure and has means for releasing or discharging the blastingmedium upon predetermined conditions, and concentrating and directingthe discharged fluid in a predetermined direction or directions.

This invention relates particularly to the type of cartridge shown inthe applicants copending application, Serial No. 169,441, filed February19, 1927, for improvements in blasting cartridges. It will be noted thatthe .cartridge therein disclosed is one having a refillable rigid casingadapted to contain a substance gaseous at ordinary temperatures andpressures such as, for example, carbon dioxide, and is further providedwith a releasable end wall, a discharge nozzle and means forartificially and internally heating the blasting medium. In operation,the blasting medium is ignited by means of an electric current whichartificially raises the temperature of the compressed carbon dioxide toand above its critical temperature to cause the development of anexcessive pressure within the cartridge. The pressure developed isgreater than the predetermined pressure at which the end wall ruptures.By accurately adjusting the behavior of the respective parts a dischargeof the cartridge causes a rapid heating, agitation and vaporization ofthe carbon dioxide, the development of excessive pressure and therelease of the end wall, and the concentration and directing of thedischarging gases in a substantially in-' stantaneous time interval.

One of the objects of the present invention is to provide a method bywhich the rigid casing for cartridges of this type may be made frommetal alloy which retains its original qualities after the formingoperation of the seamless drawn tube and one in which the undesirablecracking and lamina tion at important points, such as at the knife edes, is eliminated.

nother object is to provide a cartridge shell which has an improvedthroat or nozzle area at the discharge end, the configuration SHELL FORBLASTING CARTRIDGES 1928. Serial No. 287,864.

of which has been determined after long experiment and study and is onecausing the blasting medium in the container after gasification byartificial heat to escape from the shell in the smallest interval oftime without creating eddy currents or becoming wiredrawn toan extentwhich would diminish the velocity of efilux and cause loss of pressure.

The invention is illustrated as applied to a cartridge in which themaximum nozzling effect is obtained, and further, one in which thenozzle construction is continued into the spaces in the interior of thedischargecap, and finally to the exit holes located in the circumferenceof the discharge cap positioned at substantially 90 to the axis of thecar-.

flecting curve on its inner surface, which wall and curve serve tocounteract the initial velocity rush of the issuing blasting me dium andto deflect the gas to the exit nozzles in the cap circumference with theleast amount of friction and loss of pressure.

These and otherobjects are accomplished by means of the arrangementdisclosed on the accompanying sheet of'drawing, in which- Figure 1' is aside elevational view of a cartridge similar to that shown in thecopending application referred to and embodying the novel features ofthe present invention;

Figure 2 is an enlarged cross sectional view of the cartridge shown inFigure 1, dis closing the internal construction of the shell and capforming the nozzle.

The various novel features of the invention will be apparent from thefollowing de-.

like that. disclosed in the co-pending appli cation above referred to,the present disclosure is limited to just such parts as are necessaryfor a clear understanding of this invention, attention being directed tothe prior disclosure for the omitted parts.

By referring to the drawing, it will be noted that the present inventionrelates to a cartridge having a refillable cylindrical casing 10, havinga discharge end 11 of reduced diameter with a tapered internal shoulder12. In producing the shell for this cartridge by the improved method, itis originally formed to a shape indicated by the outline 12 as shown inFigure 2'. The inward shoulder 12 and the internal diameter of thecasing, except for the nozzle portion, are determined at the time of theinitial forming operation. There is. an excess of metal, however,provided overthe exterior of the surface and on the inside of thenozzle. The casing or barrel of the shell, by a machining operation, isfirst cut down throughout its entire length to the exterior dimension13.

By additional machining n the exterior of the discharged end the reducedportion 11 is provided forming the shoulder 14 which extends parallel tothe internal shoulder 12 and so spaced therefrom as to provide a wall ofsuitable strength and thickness and substantially equal to the wallportion of the main body of the shell or barrel. The outside of the endportion is then threaded, as shown, for receiving the cap member, andthe interior of the nozzle, which is also provided initially with excessmetal as shown in 15, is cut down to the finished surface 16. The knifeedges may then be provided by machining on the outer edge to the shapeshown in the drawing. It has been found in practice that machining themetal barrel to the shape shown, after a simple forming operation,results in unaltered metal at the locations of greatest importance, thatis at the nozzle, throat'and knife edge seals, re-

spectively.

After machining these locations are specially hardened by heat treatmentunder controlled temperatures, and. cartridges suitable for exceptionalservice are obtained by this process resulting in l ong life to therigid contamer.

By machining the reduced end, instead of swedging or otherwisehydraulically forging it, a better cartridge is produced, because in aswedging operation the end of the shell is heated only once and then themetal forced into form by machine means which tends to produce a coldworking of the metal, thus hardeningit without cont-r01 of temperature,which latter causes the metal at the place of greatest contraction orworking to split and laminate or otherwise become weakened or fracturedunder strain.

On the end of the casing 11 the cap 17 is threaded, the parts being soconstructed that the outer periphery of the cap is'a continuation of theouter cylindrical surface of the barrel. The interior of the cap isprovided with a cavity 18, nozzle portion 19 and radially disposedopenings 20 and also with a shoulder 21 for securing, when the cap is inplace, the shear ring 22, and the rupturable end wall 23 in placeagainst the knife edge or edges as shown in the drawing. The nozzleportion 19 is flared and is shaped to form a continuation of the nozzlesurface 16 in the end of the barrel. The inner surface 24 of the shearring is likewise flared to produce a continuation of the nozzle. In theparticular form therein illustrated the nozzle eflect is carried to theradial outlets 20, which are provided with flared surfaces 25 to effectan outward enlargement of the opening, it being understood, however,that this is not absolutely necessary. The end wall of the cap isprovided on the inside with the curved surface 26, which may take theform of an inwardly extending cone and may be replaceable and which isfound to produce a desirable elfect in directingthe discharging gasesout of the openings 20 and also in offering a resistance in oppositionto the opposite end wall of the cartridge for preventing bodilydisplacement of the cartridge in the drill hole upon discharge. Theopening 27 may be provided in the end wall for permitting theintroduction of a tool or other means employed for refilling thecartridges. The opening 27 is relatively small and does not impair to asubstantial extent the function assigned to the inner surface of the endwall. The particular flare of the nozzle illustrated is designed inaccordance with data secured from numerous experiments giving the properdimensions to insure the properve- I locity of eflflux of the gas sothat the container is capable of completely discharging its contentsthrough the ruptured wall or disk into the interior space of thedischarge cap in I an interval of time comparatively instantaneous.

The nozzle construction of the interior of the cap and the outletstherein allow the blasting medium to continue on its path to the drillhole without great loss in velocity and pressure which results in thedoing of maximum work in the drill hole.

The instantaneous transfer of heat from a suitableheating element to theblasting medium accompanied by violent agitation and resulting rise inpressure of the blasting medium to the rupturing strength of the wall ordisk, all as described in the c o-pending application referred to, andthe nozzling of the exit throat of the container and the likewise nozzleconstruction of the cap interior, together with the directive power ofthese exits in the application of gas pres sure on the coal or otherbody to be broken down, as well as the minimum of voids about theexterior of the shell and the drill hole, are the main-reasons for theefficient action of the blasting medium in the work of looseningmaterials. Other reasons are the large number of cubic feet of gas perpound of blasting medium, the low temperature to which it has to beheated to render it gaseous and to create a pressure sufficient torupture the wall or disk at the end of the container and the slow rateof cooling of the gaseous blasting medium due to such low temperatures.

As compared with black powder, the combustion temperature of the latteris in the neighborhood of 3500913. Its gas content is about four cubicfeet per pound, hence its rate of cooling is extremely fast. In the caseof carbon dioxide, the temperature of heating is only 400, and the cubicfeet per pound are eight, and its rate of cooling is thereforetremendously lower -than that of black powder.

The combustion temperatures of the dynamites are even higher than thefigure given for black powder, and consequently the cooling gradient isalso much steeper.

Still another factor enters in the case of carbon dioxide as blastingmedium when compared with the powders and dynamites. The specific Weightof the former when at atmospheric temperature and pressure is 1.5 timesthat of air while the gases from the combustion of the powders anddynamites in the same state is probably a little less than 1.0 orperhaps 1.0 when comparedwith air. Under the same degree of temperaturerise and pressurethe pure carbon dioxide gas will have a greater rangeof action due to its increased momentum over the gases from the otherexplosives. This accounts partly for the great penetrating and spreadingpower of the carbon dioxide gas and its pushing or prying action in coalwhilein the case of the powders the gases rather hit a blow on the coalwithout much spreading action.

It has already been mentioned in the copending application referred tothat another function of the solid end in the discharge cap and thedischarge-of the blasting medium at right angles, more or less,to themain container axis, is to cause the initial velocity rush of the gas,which is exceedingly high, to be substantially com ensated for andthereby eliminate the ten ency of the container to move backward "in thedrill hole. Movement in the drill hole is objectionable in that itcauses a large extra void to be made at the discharge end of the shelland also backing up on the conductors attached to the valve cap at thecharge end of the shell, damaging them or causing short circuit betweenthem.

It will be obvious from the above that the directing action of thenozzle openings 20 in the cap circumference causes a greater portion ofthe gasified blasting medium to be applied to the drill hole in the coalor'other body to be broken down at an angle of about 90 to the main axisof the rigid container. This gives a wider transverse area of action orapplication of the blasting medium and results in an increase inmaterial broken loose, a cleaner shear in the ribs of the coal or otherbody and a cleaner and more eflicient detachment of the coal or otherbody from the breast. In addition the deviation of a large part of theblasting medium from contact and action on the roof of the coal bodycauses the breaking and loosening action upon the roof rock and slate tobe satisfactorily light, and goes farfto diminish the maintenance costof the roo 7 It will further appear that the container is one having aconstant overall dimension which may be inserted into a drill hole cutwith a constant diameter and with small clearance over the diameter ofthe shell without excess space about the container. This elimination ofvoids or excess space about the container makes for a maximum ofefficiency in the action of the pressure exerted upon discharge. Inaddition the presence of moisture or running water in the drill hole,coal or other body to be broken down, is no detriment to the operation,but is rather an aid to the blasting operation, in that the wateraccumulates in the drill hole about the shell after it is tamped inplace and effectively fills whatever voids there happens to be present.

We claim:

1. A cartridge of the character described, having a nozzle and a cap,having an inwardly projecting rounded end wall disposed in opposition tothe end of said nozzle.

2. A blasting cartridge comprising a casing having a tapered dischargenozzle, a closure for the end of said nozzle and cap associated withsaid nozzle and having a tapered passage forming a continuation of saidnozzle.

3. A blasting cartridge comprising a casing having a discharge passage,a cap for said casing having a chamber, and a plurality of radiallyarranged tapered discharge orifices in said cap.

4. A blasting cartridge comprising a casing having a tapered dischargenozzle, a closure for the end of said nozzle, a cap associated with saidnozzle and having a tapered passage forming a continuation of saidnozzle and aplurality of radially arranged tapered outlets communicatingwith said passa e.

g. A blasting cartridge comprising a casing having a discharge openingtapering from the inside outwardly and a cap associated with said casingand having a correspondingly tapered passage forming a continuation ofsaid discharge opening.

6. A blasting cartridge embodying an outwardly tapered discharge passagewith a convex deflecting wall arranged in opposition thereto, and aplurality of radially arranged discharge ports communicatingwith saidpassage adjacent said wall.

7. A blasting cartridge comprising a casing having a tapered dischargepassage, a rupturable disc disposed over the end of said passage, ashear ring arranged adjacent said disc, and a cap adjustably connectedwith said casing and having a part engaging said shear ring, said capand shear ring being formed with a tapered passage in continuation ofthe aforesaid tapered passage.

Signed at Duquoin, Illinois, this 16th day of June, 1928.

ARTHUR W. HELMHOLTZ. DENT FERRELL.

